Tissue sections or cellular monolayers are commonly examined by microscopic examination, for both research and clinical diagnostic purposes. Thin tissue sections or cellular preparations are commonly 1-10 microns thick, and are nearly transparent if untreated. In order to visualize various histologic features, a wide array of staining procedures have been developed over the years that highlight various cellular or extracellular components of the tissues. Histochemical stains, also commonly termed "special stains," employ chemical reactions to color various chemical moieties. Immunohistochemical stains employ antibodies as probes to color specific proteins, commonly via enzymatic deposition of a colored precipitate. Each of these histochemical and immunohistochemical stains requires the addition and removal of reagents in a defined sequence for specific time periods, at defined temperatures. Therefore, a need arises for a slide stainer that can perform a diversity of stains simultaneously under computer control, as specified by the technologist.
An early slide stainer for immunohistochemistry was described by David Brigati M.D., U.S. Pat. No. 4,731,335. In that disclosure, microscope slides were closely apposed to each other, to form capillary gaps. The pairs of slides were mounted in a holder that could be moved about by a mechanical arm along three axes. If slides were to be heated, all of the slides were moved as a group into a humidified heated chamber. Therefore, random access capability is not possible with this design.
In another slide stainer by Rogers and Sullivan, U.S. Pat. No. 4,043,292, slides are mounted on a rotary carousel. Their invention heats the slides by passing a heated stream of air over the slides. All of the slides are heated to the same temperature.
Wooton, McLeod, and Read disclose another slide stainer that incorporates heat capability, in U.S. Pat. No. 5,231,029. In that invention, a steam chamber is provided to heat slides. The humidity in the steam chamber is designed to be just below 100 percent. If the slides are to be heated, they are placed into the chamber. Since the slides are either in or out of the chamber, all slides must be brought to the same heated temperature, a temperature approximately that of steam (100.degree. C.).
A recently described batch slide stainer commercialized by Ventana Medical Systems, Inc. is disclosed in U.S. Pat. No. 5,595,707 by Copeland, et. al. In that disclosure, slides are placed on a rotary carousel that allows for the addition and flushing of reagents from the slide surface. Their slide stainer includes a heating chamber that is heated by the introduction of warm air. A temperature sensor is contained within the chamber for providing temperature feedback to a microprocessor. Similar to the other slide stainers described above, all slides must be brought to the same temperature.